MRI assessment of myocardial viability: comparison with other imaging techniques

The identification of dysfunctional but viable myocardium in patients with coronary artery disease with or without a history of myocardial infarction is of paramount clinical importance since viable myocardial areas are most likely to benefit from revascularization, whereas revascularization of scar tissue will not lead to improvement of left ventricular function. In some patients cardiac catheterization itself already provides important clues to the presence of viable myocardium based on the degree of wall motion abnormalities, post-extrasystolic improvement of wall motion, the presence of collateral vessels or persisting angina in a patient with single vessel disease. However, due to the complexity of viability assessment especially in patients with severely depressed left ventricular function and multi-vessel disease, viability tests are usually requested after the results of coronary angiography are known. Among the diagnostic armamentarium to identify viable myocardium the most established techniques are single photon emission computed tomography (SPECT), positron emission tomography (PET) if available and dobutamine stress-echocardiography. With the application of magnetic resonance imaging (MRI) in clinical cardiology an important and exciting diagnostic tool has been added for the prospective identification of viable myocardium for purposes of guiding therapeutic interventions in individual patients. This article reviews comparative studies between MRI and established imaging techniques like PET, SPECT and dobutamine-echocardiography with respect to the assessment of viable myocardium in patients with acute myocardial infarction and chronic coronary artery disease.